The primary purpose of a stationary generator set (genset) is to produce electrical power directed for external use. A genset typically includes a main generator coupled to and driven by a combustion engine. As a mixture of fuel and air is burned within the engine of the genset, a mechanical rotation is created that drives the main generator to produce electrical power. Power electronics associated with the main generator then condition the electrical power according to needs of an external load. Byproducts of the combustion process are exhausted to the environment.
An amount of mechanical power produced by the engine is directly related to an electricity output capacity of the genset. For this reason, gensets are often equipped with one or more turbochargers that are driven by exhaust to compress combustion air entering the engine. By forcing air into the engine, more air becomes available for combustion than could otherwise be drawn into the engine by motion of the engine's pistons. This increased supply of air allows for increased fueling, resulting in an increased mechanical power output and a corresponding increased electrically output of the generator. A turbocharged engine typically produces more mechanical power than the same engine without turbocharging.
Unfortunately, turbochargers do not remove all of the energy contained within an engine's exhaust prior to the exhaust being discharged to the atmosphere. Thus, upon discharge to the atmosphere, some amount of energy may be wasted in the form of heat and/or pressure. If this energy could be recuperated, efficiency of the genset may be improved.
An attempt to recuperate exhaust energy in a stationary genset application is disclosed in U.S. Pat. No. 7,047,743 (the '743 patent) issued to Stahlhut et al. on May 23, 2006. Specifically, the '743 patent discloses an engine/electric generator system having an internal combustion engine, and a primary electric generator driven by an output shaft of the engine to provide electrical power. The system also includes a turbocharger having a first turbine driven by exhaust gasses from the engine, and a compressor driven by the first turbine to provide inlet air to the engine. The system further includes a secondary turbine, and an exhaust line which communicates exhaust gas from the first turbine to an input of the secondary turbine. A secondary electric generator is driven by the secondary turbine. An electric power combining circuit combines electric power from the primary electric generator and the secondary electric generator, and delivers the combined electric power to a transmission line. In this manner, energy from the exhaust may be used to generate electric power through turbo-compounding.
Although the engine/electric generator system of the '743 patent may have improved efficiency, it may still be less than optimal. Specifically, the system of the '743 patent requires a dedicated secondary turbine located downstream of and inline with the primary turbine to drive the secondary generator. The dedicated secondary turbine and associated ducting may increase a cost and a size of the system, and require complex controls for proper speed regulation of the secondary generator.
The stationary genset power system of the present disclosure addresses one or more of the problems set forth above and/or other problems of the prior art.